The couple was indicted in October in U.S. District Court on one count of conspiracy to defraud the U.S. government.

The charges were filed after state and federal agents raided the couple’s farm last year.

Authorities had warned the Verhaars not to retain unregistered foreigners after a pair of raids in 2007, Bay City Times records show.

In each instance, a dozen farm employees, age 16 to 33, were found to be in the country illegally in 2007, authorities have said.

Investigators said they believed the couple had been employing unregistered immigrants since at least 2000, court records show. At least 78 undocumented immigrants were employed, making up about 75 percent of the farm's workforce, said U.S. Attorney Barbara L. McQuade.

The couple sometimes used fraudulent Social Security numbers to employ specific people whom Immigration and Customs Enforcement agents had specifically prohibited from working at the farm, records show.

Investigators have said the Verhaars are citizens of the Netherlands who have temporary visas to work in the United States. They have lived in the Thumb and operated the farm, with about 2,500 head of cattle, for years.